New communication methods using RFID or NFC technology have been widely used recently. RFID refers to technology of reading information stored in an electronic tag in a non-contact mode wherein the reading of the information is performed through an antenna or a reader using radio waves. For example, a transportation card may be considered to be an electronic tag, and a transportation card terminal may be considered to be a reader. NFC refers to communication technology of exchanging various kinds of wireless data within a short distance of 10 cm. This technology is non-contact short-range wireless communication technology using a frequency band of 13.56 MHz. The NFC technology has been widely used for handling of information on articles in a supermarket or store, transfer of tourist information for visitors, traffic, and locking devices for access control, as well as for payment, and has a short-range communication distance. As a result, the NFC technology has attracted attention since it has relatively superior security and is inexpensive.
When a product such as a mobile phone is manufactured, a sufficient space is present between a battery and a rear cover of the product. Accordingly, an NFC/RFID loop antenna is installed in this space. In general, since a coil is mounted in the antenna, the flow of an electric current results in formation of a magnetic field, which is then allowed to transfer signals to other sides. For example, when a product such as a credit card, a smartphone, or an electronic wallet is in a dissembled state, the product is configured so that an antenna having a coil mounted therein can be installed in the product to enable the exchange of data stored in the product. However, when the antenna is installed in a battery or a printed circuit board (PCB) so that it is positioned adjacent to a conductive material such as a metal, the antenna reacts with the metal and causes interference, preventing generation of signals.
The problems regarding such interference can be effectively solved by isolating magnetism using a material exhibiting high permeability and having low permeability loss. That is, the material exhibiting high permeability allows signals to travel toward a magnetic material rather than the metal to prevent the interference of the metal. Such a material is generally referred to as an isolator. In general, ferrite is known as a material exhibiting high permeability and having low permeability loss as described above. Also, various methods of manufacturing a ferrite sheet are already known in the related art.
Ferrite sheets used recently have grooves that cross continuously in a certain pattern mode, and the grooves can be compartmentalized by the patterns designed thus. Therefore, the ferrite sheet can be easily handled, and attached to a flat or curved plane. There are many methods used to form such patterns. The most common method is a method of forming a half cut on a green sheet by means of a method using a knife. Meanwhile, a hole drilling method of forming a certain division pattern has been developed recently. Such a method can be useful in manufacturing products having a thickness of less than 0.08 mm.
US 2012/0088070 A1 discloses a composite ferrite sheet having V-shaped grooves arranged in a lattice-type mode, a method of manufacturing a composite ferrite sheet, and a sintered ferrite segment used to form the composite ferrite sheet. Also, Korean Patent Publication No. 10-2008-0082466 discloses a ferrite molded sheet having controlled surface roughness, a sintered ferrite substrate, and an antenna module. All the prior-art documents encounter difficulties in forming precise patterns since the patterns are formed by mechanically applying a pressure onto a green sheet using a knife or drum. Also, since a separate mechanical process is further performed to form the patterns, these processes may be long and complicated, and a bottleneck state may be caused during the entire processes since the separate mechanical process should be performed for a long period of time. In addition, burrs, which are pieces that are broken during a process and are inevitably formed in a mechanical process, necessarily occur in the manufactured ferrite sheet itself, and a situation in which particles break off and are stuck on the ferrite sheet itself may not be avoidable. Further, the shape and size of the grooves cannot be easily controlled since the grooves are formed using the mechanical process.